Well I'm not going to sit here and say this is the way to do it, but it is my ritual that works for me. Every time I wash my car, I clean the wheels also and while drying, I use Griot's Garage Spray-On Wax on all body and wheel surfaces. I'm not sure how much help it is in keeping the wheels clean, but I don't have a lot of buildup just before washing.
Griot's Garage Spray-On Wax